Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$111.47	10.568%	$123.2501	$123.25	$123.25	$123.30
Purchase #2	$152.98	12.334%	$171.8486	$171.85	$171.85	$171.80
Purchase #3	$152.28	4.724%	$159.4737	$159.47	$159.45	$159.50
Purchase #4	$241.90	12.280%	$271.6053	$271.61	$271.60	$271.60
Purchase #5	$42.68	7.787%	$46.0035	$46.00	$46.00	$46.00
Purchase #6	$51.93	8.325%	$56.2532	$56.25	$56.25	$56.30
Purchase #7	$71.80	3.169%	$74.0753	$74.08	$74.10	$74.10
7 purchase totals =	$825.04		$902.5097	$902.51	$902.50	$902.60